Semiconductor Physics, Quantum Electronics & Optoelectronics. 2000. V. 3, N 3. P. 394-399.

PACS: 78.30L, 78.66.J, 81.05.Gc

Photoinduced structural changes in As_100-xS_x layers

A. Stronski^a, M. Vlcek^b, A. Sklenar^b

a Institute of Semiconductor Physics, NAS, Kiev, 252028, Ukraine
b University of Pardubice, 532 10 Pardubice, Czech Republic

Abstract. The present paper is concerned with investigations of photoinduced structural changes in As100-xSx layers. Optical constants of variously treated (virgin, exposed, annealed) samples were determined from optical transmission measurements in the spectral region 400-2500 nm. The energy dependence of refractive index n for variously treated samples was fitted by the Wemple-DiDomenico dispersion relationship and used to estimate the single-oscillator model parameters. It was found, that exposure, as well as annealing leads to the increase in n values over the all investigated spectral region. Compositional dependencies of single-oscillator model parameter Ed (dispersion energy), optical dielectric constant e(0) show maximum at stoichiometric composition As₄₀S₆₀ and, possibly, weak maximum at As_28.6S_71.4 composition. Changes of the parameters of the single-oscillator model induced by treatment are discussed on the base of photo- and thermally-induced structural changes, which were directly confirmed by Raman scattering measurements. Such photoinduced structural changes provide good etching selectivity of As-S layers in amine based solvents. Intensity dependence of the Raman bands corresponding to the As rich and S rich molecular fragments on exposure time is well described by the exponential decay, which correlates with exponential decay dependence of the etching rate of As_100-xS_x layers on exposure.

Keywords: As-S layers, optical properties, Raman spectra.

Paper received 19.01.00; revised manuscript received 08.05.00; accepted for publication 06.06.00.

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